1. Technical Field
The present invention relates, in general, to an Ultra-WideBand (UWB) distance measurement system and a method of driving the system, and, more particularly, to a distance measurement system using UWB communication and a method of driving the system, which can improve the efficiency of vehicle traveling and intelligent transportation systems.
2. Related Art
Recently, as communication technology is applied to various fields, new types of services have been actively provided. Among these services, Intelligent Transportation Systems (ITS) in which wireless communication technology, such as Ultra-WideBand (UWB) technology, and distance measurement technology are combined with each other for improving the efficiency of vehicle traveling and transportation systems have recently been provided, and the development of technology related to ITS has been actively conducted.
In current wireless communication fields, a demand for frequency has rapidly increased compared to limited frequency resources. As one method of solving this problem, a UWB communication method capable of more efficiently utilizing frequency resources by sharing the frequency spectrum of existing communication systems has attracted attention.
Such a UWB communication method is a wireless transmission technology for transmitting digital data at ultra-wideband frequencies using very low power, and enabling reliable communication by constructing ultra high-speed and high-performance wireless networks using very low power. Further, a UWB communication method has been widely used in equipments having low intercept and detection probability, collision prevention equipments for vehicles and aircraft, altimeters for measuring altitude above the earth's surface in airplanes and other airline facilities, and important national defense technologies and public fields specially requiring secure communication, such as location tracking.
In the case of UWB signals, which are transmitted in the form of wideband pulses, as signals having a short pulse width are sequentially transmitted, mutual interference between the signals is decreased, thus enabling the transmission performance of signals to be maintained in a multi-path environment. Since a UWB communication method facilitates the precise resolution of multiple paths thanks to the use of ultrashort pulses, it can also be applied to location tracking fields having reception diversity and accuracy of several cm.
Standards for such a UWB communication method were established by the U.S. Federal Communications Commission (FCC) in 2002. The standards limit the transmission power and spectrum of UWB indoor and outdoor communication systems.
The U.S. FCC permits the occupation of a frequency band ranging from 3.10 GHz to 10.60 GHz having a power spectrum density of −41.3 or less [dBm/MHz] for the UWB communication method. Since a UWB communication method uses a wide frequency bandwidth, as described above, it can be applied to various application fields. Thanks to this advantage, a UWB communication method has been applied especially to distance measurement fields enabling the relative distance between radar terminals to be accurately measured among various application fields.
In a UWB communication method, since required power per unit bandwidth is very low due to ultra-wideband characteristics, and, as a result, power consumption is low and large channel capacity is provided, the UWB communication method can support a large amount of data processed and a high transfer rate, compared to existing communication systems.
However, the advantage of a transmission stage in the UWB communication method may result in a problem in that a reception stage must process a procedure for detecting that signals having the form of ultrashort pulses are received at the very low level of intensity and synchronizing the signals at regular intervals of several nanoseconds. Further, a pulse-type UWB communication method that uses the extremely short duration of time pulses, having an extremely high peak value compared to an average rate, is disadvantageous in that, when a communication system is designed to be operated in a high frequency bandwidth at a low data rate, hardware problems such as the nonlinearity of power amplification are caused.
Therefore, the improvement of reliability of a useful and efficient UWB communication method greatly influences the utilization of location tracking and distance measurement systems which use a UWB communication method.
Distance measurement methods using a UWB communication method are mainly classified into a UWB-Impulse Radio (IR) method and a UWB-chirp method.
The UWB-IR method is problematic in that, since transmission power must be increased so as to increase measurable distances and measurement accuracy, instantaneous peak power is also increased when transmission power is increased. In order to increase transmission power without increasing instantaneous peak power, a temporally longer signal must be used. Therefore, there has been proposed the UWB-chirp method of measuring distance between objects using a chirp waveform which has a temporal length at least 10 times as long as that of the monocycle waveform of the UWB-IR method and has characteristics identical to those of the monocycle waveform.
The UWB communication method using such a chirp waveform is advantageous in that it uses a modulated waveform having a long duration without resulting in a high peak value compared to an average rate, thus enabling the system to avoid the nonlinearity of a power amplifier.
However, such a UWB communication method using a chirp waveform is problematic in that great Narrow Band Interference (NBI) occurs in a band due to the use of wideband frequencies which are basic characteristics of UWB. NBI in such a UWB communication method causes great difficulty when those skilled in the art design communication systems. In particular, in a distance measurement system using a UWB communication system, the reliability of distance measurement is greatly influenced by the reliability of communication. Accordingly, there is a need for a UWB communication method capable of improving reliability by decreasing the influence of NBI on a frequency band and a UWB distance measurement system using the UWB communication method.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.